In a large skillet over medium/high heat, brown the ground beef until almost cooked through.
Add onion, then continue to cook until beef is browned and onion is cooked through.
Add taco seasoning and mix well.
Add tomatoes and frozen cauliflower/broccoli mixture and stir to combine well.
Add the broth and stir well.
Reduce heat to low, cover the pan with a lid, and simmer for another 3-5 minutes or until veggies are cooked through.
Sprinkle cheese over the meat mixture and cover with the lid for another 3-5 minutes or until cheese is melted.
Serve with sour cream, green onions, and avocado.